1. Field of the Invention
The present invention relates to a display device which can be installed outdoors.
2. Description of Related Art
Conventionally, flat type displays such as a liquid crystal display are widely used. Most of the conventional flat type displays are designed for indoor installations, and the measures to protect them from the environmental condition such as a rainstorm, dust etc. are not taken. Therefore, when displays are permanently installed outdoors, and a trouble may occur in the display panel or the circuit board because the panel or the circuit board is disposed to rainstorm etc.
In view of this, it was considered to arrange the display panel and the circuit board in a sealed casing in order to protect them.
However, when the display panel and the circuit board are arranged in a sealed casing, heat generated from the display panel or the circuit board stays inside the casing, and the temperature in the casing increases. Accordingly a trouble may possibly occur in the display panel or the circuit board.
Further, when these displays are installed outdoors, a temperature of the image display screen of the display panel increases because of the sunlight. As a result, a trouble may occur in the display panel, for example, a “blackout”. The blackout is a phenomenon in which the liquid crystal panel cannot display an image when a liquid crystal in the liquid crystal panel loses its orientation due to the temperature increase.
In view of this, it was considered to provide a cooler for cooling the air inside the casing and a fan for circulating the cooled air, and flow the air cooled by the cooler into a gap between the image display screen of the display panel and the glass plate provided to the casing.
On the other hand, when the temperature of the image display screen falls, it is considered to stop the cooling of the air by the cooler.
However, if only the cooler is deactivated while keeping the fan activated, the air is warmed by the heat generated from the display panel or the circuit board, and the warmed air is flown between the image display screen and the glass plate. Therefore, moisture in the air is precipitated due to a temperature difference between the cooled glass plate and the warmed air. As a result, dew condensation occurs on a rear surface of the glass plate, and a viewability of the image display screen of the display panel is deteriorated.